<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>正则扩展-反向断言</title>
  </head>
  <body>
    <script>
      //声明字符串
      let str = "JS5211314你知道么555啦啦啦";
      //正向断言
      //   const reg = /\d+(?=啦)/;
      //   const result = reg.exec(str);

      //反向断言
      const reg = /(?<=么)\d+/;
      const result = reg.exec(str);
      console.log(result);
    </script>
  </body>
</html>
